All combat combines both defense and offense. However the traditional battlefield has almost always had a safe rear area to provide for the fighting forces. Current weaponry and support vehicles have been designed following this age old pattern: The fighting equipment and men defend the support equipment and men. Armored vehicle technology has been exclusively the domain of the Armored Fighting Vehicle. Armored fighting vehicles (AFVs), both tanks and armored personnel carriers (APCs), first saw limited use in World War I. These early AFVs were little more than crude armor boxes built on caterpillar-tracked tractors. Both armor and weaponry have escalated dramatically since then.
In the early 1930s, shaped-charged warheads were developed that offered vastly superior armor penetrating performance coupled with ease of use and employment. The basic principle of the shaped-charge warhead is a concave or cone shaped hollow area in one end of the explosive core of the warhead. This hollow area is lined with a metal, typically copper. Upon detonation, the metal liner is compressed into a jet of very dense, superplastic metal moving at a speed of approximately 30,000 feet per second. While the actual material properties and physical behaviors are still not very well understood, the hypervelocity jet of metal can punch a hole in steel plate armor many times thicker than the diameter of the shaped-charge warhead.
Detonation distance is critical because the jet disintegrates and disperses after a relatively short distance (no more than 2 meters typically). The critical factor to the effectiveness of a HEAT round is the diameter of the warhead. As the jet penetrates the armor, the width of the hole decreases leading to a characteristic “fist to finger” penetration effect. That is, the size of the eventual “finger” penetrating into the AFV depends on the size of the original “fist”. In general, a HEAT round will penetrate armor thickness 150% to 250% of their diameter, although modern versions, such as the latest Russian RPG-7V, claim penetration ratios as high as 700% of the warhead diameter.
By the end of World War II, various anti-tank weapons had been developed and deployed that could be carried by one man to defeat AFVs, including hand-thrown grenades (e.g. Russian RPG-43) and warheads mounted on a rocket and launched from a rocket launcher (e.g. United States M7A1—“Bazooka”). Since World War II, HEAT rounds have become almost universal as the primary anti-vehicle weapon, because it can be used against all AFV and unarmored targets such as trucks and other general purpose vehicles or bunkers.
In modern warfare, man-portable anti-tank weapons represent one of the greatest threats on the battlefield. These weapons are relatively light, easy to transport, and can defeat most AFV armor if the AFV is struck in a vulnerable location. The Soviet RPG-7 is probably the most ubiquitous of these weapons, because it has been produced by most Soviet client states including all of the former Warsaw Pact countries, Egypt, Libya, Iraq, Iran, China, North Korea, and numerous other countries, and it has been widely disseminated by these numerous producing countries. The RPG-7's maximum effective range against moving targets is 300 meters and the maximum range is 920 meters, and it can penetrate up to 600 millimeters (23 inches) of rolled homogeneous steel armor.
In the technology race of anti-tank weaponry versus armor protection, AFV armor protection technology has attempted to match increased lethality. Armor protection has improved dramatically and increasing use has been made of more unconventional means to increase protection. One of the unconventional modifications used in unconventional combat has been the use of standoff screens around a fighting vehicle to prevent shaped charges from detonating against the vehicle armor. Sand bags have also served as additional armor as have water cans. While many of these armor advances have been proven effective and have been deployed on heavy AFVs, there has been virtually no effort to protect lighter non-combat vehicles such as trucks and the M998 HMMWV family of vehicles. While the M998 series has been modified with additional armor to increase protection against large caliber bullets and land mines, there has been little progress at protecting these rear echelon support vehicles from light anti-tank HEAT warheads, since it was believed that they were going to be protected by the fighting vehicles in the historic battlefield configuration.
Similar concerns apply to military aircraft. With dawn of the transistor age and silicon chip technology coupled with advances in solid-fuel rocket booster technology, man portable air defense systems (MANPADS) based on small, light-weight surface-to-air missiles (SAMS) have proliferated greatly over the years.
The United States pioneered the development of MANPADS with the introduction of the RIM-43 Redeye SAM in 1966. The Redeye was developed in the 1950s and is a heat-seeking missile that senses the exhaust heat from the engines and directs the missile toward that heat source. Modern MANPADS predominately are small, shoulder-fired, infrared seeking SAMs that home in on the infrared energy emissions of the target aircraft. They are effective against jet, propeller, or rotor (e.g. helicopter) aircraft. There are an estimated 500,000 MANPADS in existence.
Currently, the following are the most prevalent MANPADS:
1) Strela-2 (SA-7a): Soviet designed IR guided SAM that can engage aircraft flying above 50 meters and below 1500 meters. The warhead detonates upon impact with the target.
2) Strela-2M (SA-7b): Improved guidance over the earlier Strela-2 allows the missile to engage transport and rotor aircraft head-on as long as the target speed is less than 540 km/hour. The missile target ceiling is 2300 meters and can engage targets out to 4.2 km.
3) Strela-3 (SA-14): The SA-14 entered service in 1974. Possesses an improved IR seeker allowing engaging jet aircraft head-on and reducing effectiveness of flare countermeasures. Can effectively engage target within an altitude limitation of 30 meter to 3000 meters.
4) Igla-1 (SA-16) and Igla-2 (SA-18): Soviet SAM equipped with both a proximity and an impact fuse. Maximum range of 5.2 km and can engage targets in the altitude range between 10 meters and 3500 meters.
5) FIM-92 (Stinger): US manufactured SAM having a range of 4.8 km. Has a maximum speed of Mach 2.2.
Other MANPADS include the Swedish Bofors RBS-70, the British Shorts Blowpipe and Javelin.
All of these SAMs are somewhat hampered by the small high explosive warhead, which is designed to explosively project shrapnel into a target aircraft. However, the small warhead can cause significant damage to any aircraft and is effective against both civilian and military aircraft, and the small missiles are of primary concern for military helicopters operating against guerrilla insurgencies or terrorist organizations. At least 27 guerrilla or terrorist organizations are believed to possess these weapons.
The current situation faced by United States military forces in Iraq and Afghanistan, as well as likely military deployments in the future, has underscored the reality that rear echelon, support forces and their attendant vehicles are more likely, because of this vulnerability, to come under fire from light anti-tank weapons. Various irregular combatants are increasingly attacking support and rear echelon areas and bringing light vehicles under fire with RPGs and improvised munitions, such as artillery shells rigged as command-detonated mines. There is also an increasing threat to low-flying helicopters or jet aircraft engaging ground targets or landing at airfields, where they are flying within the altitude engagement zone, from attacks from most MANPADS. There is a need for a robust, light armor system that can be retrofitted on existing vehicles and aircraft or be incorporated into new designs to provide effective HEAT or MANPADS SAM warhead protection without a prohibitive weight penalty.